Modification and modeling of water ingress in limestone after application of a biocalcification treatment

• Untreated and bio-treated samples of building limestone were subjected to water imbibition tests.
• Changes to the water transfer properties of the stone, attributable to the bio-treatment, were measured and quantified.
• A model for water transfer under these conditions is proposed, differing from the standard Washburn law.
• Bio-treatment has a limited service life over the period of the experimental run.

Water transfers have been recognized as the main vectors of alteration and are responsible for pore network modifications in building stone. Among the techniques used to limit or stop the penetration of water into the stone, the calcification properties of bacteria have been investigated and used to treat buildings. In this article we study the effect of such a treatment following a protocol used in situ. The effects of this biotreatment on limestone (here tuffeau) were measured over a large number of drying–imbibition cycles. As the imbibition curves did not follow the usual Washburn law, a model based on a space-dependent permeability coefficient is proposed. It leads to a non-linear diffusion model which accounts for the deviation from the standard Washburn model.